A moving trajectory display device is disclosed in JP-A-H08-278150. The device writes data of a position of a vehicle at every first traveling distance in a traveling trajectory memory so that the memory stores the traveling trajectory. The first traveling distance is 160 meters. Then, the traveling trajectory is overlapped on a map so that the device displays the trajectory over the map image on a display screen. When a traveling direction is changed by a predetermined angle or more, and the vehicle travels the second traveling distance from a position, at which the device previously wrote the data in the memory, the device writes the current position in the memory even if the vehicle does not travel the first traveling distance from the position, at which the device previously wrote the data in the memory. Here, the second traveling distance is 40 meters. Accordingly, when roads in a narrow area are confusing like a maze, i.e., when the roads are crossed at short distances, the device writes the data at short intervals, and the device displays the traveling trajectory. Thus, even when the vehicle drives in the region in which the roads are confusing like a maze, the device correctly displays the traveling trajectory.
In the above device, when the traveling direction is changed by a predetermined angle or more, the device writes the current position in the memory at every second traveling distance, regardless of a scale of the map displayed on the display screen. Further, the device displays the traveling trajectory. Accordingly, when the scale of the map is comparatively small, circles for showing the traveling trajectory are densely displayed on the map, and therefore, it is, hard to see the traveling trajectory.
Here, when the device does not switches from the first traveling distance to the second traveling distance so that the device writes the data in the memory at every first distance, the distance between the circles for showing the trajectory becomes wide. Therefore, the reduction of identification of the circles is improved. However, in this case, it is difficult to determine the actual trajectory.